BRUNSWICK, Maine — Running in swim flippers isn’t so hard, according to recent Brunswick High School graduate Zach Miller. You just have to lift your feet a little higher.

On Tuesday night, Miller, 18, strapped some old flippers he found in his parents’ basement onto his size 10 feet and headed out to the track behind his alma mater. Five minutes and 48 seconds later, he’d broken a world record for running a mile in swim flippers, crossing the finish line nearly 2 minutes faster than Guinness World Record holder Ashrita Furman of the United States.

Miller’s flipper-footed feat must survive a rigorous Guinness World Record authentication process before he can officially claim the title of “world record holder.”

Miller, who ran 800 meters and the mile for Brunswick High School’s track team, didn’t train in flippers. In fact, Tuesday was only the fourth time he’d run while wearing them.

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With running shoes instead of flippers, Miller’s best time in the mile is 4 minutes, 52 seconds.

Miller’s research in finding a record to break took longer than his training. After browsing the Guinness World Record website last fall, he decided running a mile in swim fins would be easier than running a mile backwards.

Last fall, he ran his first flippered mile, which clocked in at 6:17, he said Wednesday. But soon the snow fell and then track season began, so he held off on his record attempt.

Last Sunday, Miller ran a 6:10 mile in the 21-inch flippers, which must be twice as long as his feet, according to Guinness.

“I think yesterday and Sunday I definitely ran more efficiently than I did in the fall,” he said. “In the fall, I remember it was just exhausting, because my form was really awkward. But this week it was basically how I run normally — I just lifted my feet a little higher.”

Miller said he has no plans to break any other records. This summer, he’s working at Orange Leaf at Cook’s Corner. In the fall, he will head to the Rochester Institute of Technology, where he plans to study computer engineering.

First, though, he’ll pack videotape, photos and witness statements in a box, which he will ship to Guinness headquarters in London. He expects to hear confirmation of his world record within three months.

Despite his improved form, Miller said he has no thoughts of continuing his swim flipper running career.

“The pair of flippers I have gave me blisters,” he said. “If I wanted to continue training with them, I’d have to find some new flippers.”